Methods of generating hydrogen gas and power

ABSTRACT

A hydrogen generator and a fuel cell system including a fuel cell battery and the hydrogen generator. The hydrogen generator includes a cartridge, a housing with a cavity to removably contain the cartridge, and an initiation system. The cartridge includes a casing; a plurality of pellets including a hydrogen containing material; a plurality of solid heat transfer members in contact with but not penetrating the casing; a hydrogen outlet in the casing; and a hydrogen flow path from each pellet to the hydrogen outlet. A plurality of heating elements is disposed inside the housing. When the cartridge is in the cavity, each heating element is disposed so heat can be conducted from the heating element and through the casing and corresponding heat transfer member to initiate the release of hydrogen gas. The initiation system can selectively heat one or more pellets to release hydrogen gas as needed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/551,487, filed Oct. 26, 2011, entitled Hydrogen Generator and of U.S.Provisional Application No. 61/555,329, filed Nov. 14, 2011, entitledHydrogen Generator with Replaceable Fuel Unit.

TECHNICAL FIELD

This invention relates to a hydrogen generator for providing hydrogengas and a system, such as a fuel cell system, including the hydrogengenerator.

BACKGROUND

Interest in fuel cell batteries as power sources for portable electronicdevices has grown. A fuel cell is an electrochemical cell that usesmaterials from outside the cell as the active materials for the positiveand negative electrode. Because a fuel cell does not have to contain allof the active materials used to generate electricity, the fuel cell canbe made with a small volume relative to the amount of electrical energyproduced compared to other types of batteries.

Fuel cells can be categorized according to the type of electrolyte used,typically one of five types: proton exchange membrane fuel cell (PEMFC),alkaline fuel cell (AFC), phosphoric-acid fuel cell (PAFC), solid oxidefuel cell (SOFC) and molten carbonate fuel cell (MCFC). Each of thesetypes of fuel cell can use hydrogen and oxygen as the active materialsof the fuel cell negative electrode (anode) and positive electrode(cathode), respectively. Hydrogen is oxidized at the negative electrode,and oxygen is reduced at the positive electrode. Ions pass through anelectrically nonconductive, ion permeable separator and electrons passthrough an external circuit to provide an electric current.

In some types of hydrogen fuel cells, hydrogen is formed from ahydrogen-containing fuel supplied to the negative electrode side of thefuel cell. In other types of hydrogen fuel cells, hydrogen gas issupplied to the fuel cell from a source outside the fuel cell.

A fuel cell system can include a fuel cell battery, including one ormore fuel cells (such as in a fuel cell stack), and a gas source, suchas a gas tank or a gas generator. Gas generators that supply gas to afuel cell can be an integral part of a fuel cell system, they can beremovably coupled to the fuel cell system, or they can includereplaceable components containing reactants. A removable gas generatorcan be replaced with another one when the gas producing reactants havebeen consumed. Removable gas generators can be disposable (intended foronly a one-time use) or refillable (intended for use multiple times) toreplace consumed reactant materials.

Hydrogen generators can produce hydrogen using a variety of hydrogencontaining materials and a variety of methods for initiating the releaseof hydrogen therefrom. Hydrogen gas can be evolved when a hydrogencontaining material reacts. Examples of hydrogen containing materialsinclude liquid or gaseous hydrocarbons (such as methanol), hydrides(such as metal hydrides and chemical hydrides), alkali metal silicides,metal/silica gels, water, alcohols, dilute acids and organic fuels (suchas N-ethylcarbazone and perhydrofluorene). A hydrogen containingcompound can react with another reactant to produce hydrogen gas, whenthe reactants are mixed together, in the presence of a catalyst, heat oran acid, or a combination thereof.

In selecting reactants for use in a hydrogen generator, considerationmay be given to the following: (a) stability during long periods of timewhen the hydrogen generator is not in use, (b) ease of initiation of ahydrogen generating reaction, (c) the amount of energy that must beprovided to sustain the hydrogen generating reaction, (d) the maximumoperating temperature of the hydrogen generating reaction, and (e) thetotal volume of hydrogen that can be produced per unit of volume and perunit of mass of the reactant(s).

Some hydrogen containing compounds can be heated to evolve hydrogen in achemical decomposition reaction. A hydrogen generator using such typesof reactants can be advantageous with regard to the volume of hydrogenthat can be produced compared to other types of hydrogen generators suchas those with a liquid reactant.

An object of the present invention is to provide a hydrogen generatorwith one or more of the following features: inexpensive and easy tomanufacture, safe to store and use, able to produce a large total volumeof hydrogen gas per unit of mass and per unit of volume of the hydrogengenerator, able to control the supply of hydrogen on an as needed basis,able to operate at or below a desired maximum temperature, at least aportion of the hydrogen generator in a fuel cell system can be replacedafter hydrogen containing materials have been consumed, and durable andreliable for a long period of time.

SUMMARY

In one aspect of the invention, there is provided a hydrogen generator,the hydrogen generator including a cartridge, a compartment configuredto removably contain the cartridge, and an initiation system. Thecartridge includes a casing; a plurality of pellets, each comprising atleast one material capable of releasing hydrogen gas when heated; aplurality of solid heat transfer members, each in direct contact withbut not penetrating the casing and capable of conducting heat from thecasing to the at least one hydrogen containing material; a hydrogenoutlet in the casing; and a hydrogen flow path from each fuel pellet tothe hydrogen outlet. The compartment includes a housing with a wall; ahydrogen outlet through the housing; a cavity within the housing withinwhich the cartridge can be disposed; and a plurality of heating elementsdisposed within the housing, such that when the cartridge is disposedwithin the cavity each heating element is in contact with an outersurface of the cartridge casing and disposed so that heat can beconducted from the heating element, through the casing and to a heattransfer member, which can conduct the heat to a portion of the at leastone hydrogen containing material not in contact with the casing. Theinitiation system includes the heat transfer members, the heatingelements, and circuitry for conducting an electric current to theheating elements, such that the electrical current can be appliedselectively to one or more heating elements for generating heat toselectively heat one or more pellets to initiate a release of hydrogengas. Embodiments can include one or more of the following features:

-   -   the cartridge has a cylindrical shape;    -   the cartridge has a prismatic shape;    -   the cartridge and the compartment cooperate so the cartridge can        be inserted into the compartment only such that the heating        elements and the heat transfer members are aligned for        conducting heat from the heating elements, through the casing to        corresponding heat transfer members;    -   the plurality of pellets is disposed in a plurality of layers;        each layer can include a plurality of pellets;    -   the plurality of pellets is disposed in a single layer;    -   at least a portion of each heat transfer member is disposed on a        pellet surface;    -   the heat transfer members are partially disposed within the        pellets;    -   each heat transfer member has a cartridge casing contact        portion;    -   each heat transfer member includes aluminum;    -   each heat transfer member includes a layer of pyrolitic carbon        in contact with a pellet;    -   the heat transfer members are in pressure contact with an inside        surface of the casing;    -   the pellets are disposed in one or more layers and a thermally        insulating material with a thermal conductivity of less than 10        watts/(meter·Kelvin) is disposed between adjacent pellets in a        layer of pellets; a layer of the thermally insulating material        can separate adjacent layers of pellets; pellet surfaces can be        coated with a layer of the thermally insulating material;    -   the portion of the cartridge casing that makes contact with the        heating element comprises stainless steel or aluminum;    -   the housing includes a material with an electrical conductivity        at 293° K of less than 10⁻¹⁰ ohm⁻¹·meter⁻¹ and a thermal        conductivity of less than 10 watts/(meter·Kelvin);    -   the heating elements are disposed on an inside surface of at        least one of the wall and the lid the housing;    -   the heating elements make pressure contact with the outer        surface of the cartridge casing when the cartridge is disposed        within the compartment;    -   the cartridge includes means for maintaining contact between the        heat transfer members and the pellets as the hydrogen generator        is being used;    -   the cartridge includes means for maintaining a desired alignment        between the heat transfer members and the heating elements as        the hydrogen generator is being used;    -   the hydrogen flow path includes a channel extending through all        layers of pellets; the hydrogen flow path can include a central        channel; the hydrogen flow path can comprise more than one        channel;    -   at least one filter is disposed in the hydrogen flow path;    -   the cartridge is enclosed in the casing prior to the cartridge        being disposed in the cavity; the cartridge can be sealed in the        casing prior to the cartridge being disposed in the cavity; the        cartridge can include a foil seal over the hydrogen outlet valve        prior to insertion of the cartridge into the compartment; the        foil seal can be broken upon insertion of the cartridge into the        compartment;    -   the at least one hydrogen containing material is selected from        the group consisting of a material that can absorb and desorb        hydrogen and a material that can react to produce hydrogen gas        upon thermal decomposition;    -   the pellets further include an ignition material, preferably at        least one material capable of reacting exothermically selected        from the group consisting of metal/metal oxide multilayers, a        metal/metal multilayered thin film, an autoignition composition,        a gel of a metal and water, and a gel of metal and water in        combination with sodium borohydride; and    -   the pellets do not contain a catalyst for the release of        hydrogen gas.

In another aspect of the invention, there is provided a fuel cell systemincluding a fuel cell battery and a the hydrogen generator as describedabove. Embodiments can include one or more of the following features:

-   -   a portion of the initiation system is outside the hydrogen        generator; and    -   the initiation system is configured to monitor at least one of        temperature and pressure and selectively heat one or more        pellets to provide hydrogen gas as needed by the fuel cell        battery.

Unless otherwise specified, the following definitions and methods areused herein:

-   -   a solid heat transfer member is heat transfer member that is not        hollow and cannot be used to transport a fluid heating medium        therethrough;    -   a thermally insulating material is a poor conductor of heat; a        poor conductor of heat has a thermal conductivity of less than        10 watts/(meter·Kelvin), preferably less than 1        watt/(meter·Kelvin);    -   a poor electrical conductor has an electrical conductivity at        293° K of less than 10⁻¹⁰ ohm⁻¹·meter⁻¹; and    -   penetrate means to pass through (e.g., between inner and outer        surfaces or from one side to another side such as through a seam        or joint).

Unless otherwise specified herein, all disclosed characteristics andranges are as determined at room temperature (20-25° C.).

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partial sectional perspective view of a hydrogen generatoraccording to a first embodiment;

FIG. 2 is a partial sectional perspective view of the hydrogen generatorin FIG. 1, with the cartridge not inserted into the chamber;

FIG. 3 is an enlarged portion of the hydrogen generator in FIG. 1

FIG. 4 is a partially exploded perspective view of a hydrogen generatoraccording to a second embodiment;

FIG. 5 is a cross-sectional view of an individual pellet of the hydrogengenerator in FIG. 1;

FIG. 6 is a partially exploded perspective view of a hydrogen generatoraccording to a third embodiment;

FIG. 7 is a partially exploded perspective view of a cartridge for usein the hydrogen generator in FIG. 6;

FIG. 8 is a perspective view of a pellet and a heat transfer member,before assembly;

FIG. 9 is a perspective view of the pellet and heat transfer member inFIG. 8, after assembly;

FIG. 10 is a partially exploded perspective view of a hydrogen generatoraccording to a fourth embodiment;

FIG. 11 is a perspective view of a portion of a cartridge of thehydrogen generator in FIG. 10;

FIG. 12 is a partially exploded perspective view of a portion of thecartridge of the hydrogen generator in FIG. 10;

FIG. 13 is an exploded view of a portion of the cartride of the hydrogengenerator in FIG. 10;

FIG. 14 is a perspective view of an individual pellet and heat transfermember of the hydrogen generator in FIG. 10;

FIG. 15 is a perspective view of an alternative embodiment of anindividual pellet and heat transfer member of the hydrogen generator inFIG. 10;

FIG. 16 is a cross-sectional plan view of the hydrogen generator in FIG.10;

FIG. 17 is a cross-sectional plan view of an embodiment of a hydrogengenerator; and

FIG. 18 is a cross-sectional view of the hydrogen generator in FIG. 17,taken though 18-18.

DETAILED DESCRIPTION

The hydrogen generator produces hydrogen gas. The hydrogen gas can beused by a hydrogen consuming system, such as one including a fuel cellbattery that produces electricity for an electronic device. The hydrogengenerator includes a compartment into which a replaceable cartridge canbe removably inserted. It is generally desirable to include reusablecomponents in the compartment or elsewhere in the system outside thecartridge. In this way the hydrogen generator can be reused at a minimaladded expense by replacing the cartridge in which hydrogen containingmaterials are contained. The cartridge can be disposed of after use, itcan be reused by refilling it with fresh materials, or it can berecycled. The size and shape of the cartridge and the compartment can bevaried depending on the circumstances. For example, the cartridge canhave a generally cylindrical shape, or it can have a generally prismaticshape. More than one cartridge can be contained within the hydrogengenerator at one time, either in a single cavity or in more than onecavity.

The cartridge has a casing. The casing can enclose the cartridge or be asealed casing prior to insertion into the hydrogen generatorcompartment. One or more hydrogen containing materials are contained ina solid composition that is disposed in a plurality of solid bodieswithin the casing. The hydrogen containing material in the solid bodiescontains elemental hydrogen that is released as hydrogen gas when thematerial is heated sufficiently. Heat is conducted from heating elementsin contact with an outer surface of the cartridge casing, through thecasing and a plurality of solid heat transfer members to the hydrogencontaining material, thereby causing the material to release hydrogengas. The hydrogen gas released travels through a hydrogen flow path fromeach of the solid bodies to a hydrogen outlet valve in the casing.

The solid bodies containing the hydrogen containing material can be invarious forms, such as pellets, tablets, wafers, cakes, briquettes,coatings, and so on. Hydrogen containing materials and optionalcomponents of the solid composition are described below. The solidbodies can have various shapes, such as circles, ovals, squares,rectangles, trapezoids, wedges, irregular shapes, and so on. The solidbodies can be made using a suitable process, such as molding, extruding,depositing, briquetting, coating, printing, and so on. As used below,the term “pellet” refers to a solid body containing the hydrogencontaining material, and is not limited to a particular form, shape ormethod of manufacture unless otherwise stated. The pellets can be sizedand shaped to fit into the housing in a volume-efficient manner. Thepellet size and composition can be chosen to provide a desired quantityof hydrogen from each pellet, based on the size of the fuel cell batteryand the power requirements of the electronic device, for example.

The hydrogen containing material or materials, which can be referred toas fuel, are contained in a solid composition that can release hydrogengas when heated. Examples include materials that can reversibly absorband desorb hydrogen (e.g., metal-organic frameworks (MOFs), zeolites,graphene, carbon nanotubes and metal hydrides as AB₅ and AB₂ typehydrogen storage alloys such as titanium-manganese, mischmetal-nickel,lanthanum-nickel-cobalt and lanthanum-nickel alloys), materials that canreact to produce hydrogen gas upon thermal decomposition (e.g., metalhydrides such as lithium hydride, magnesium hydride, and aluminumhydride (alane), complex hydrides and their ammonia adducts such aslithium borohydride, sodium borohydride, magnesium borohydride, calciumborohydride, amine titanium (III) borohydride, lithium aluminum hydride,sodium aluminum hydride, lithium amide, and calcium aluminum hydride,and B-N chemical hydrides such ammonia borane and hydrazine borane), andvarious combinations including the above materials.

The pellets can contain one or more additives. Examples of additivesinclude binders (e.g., acrylates and styrene block copolymers),stabilizing compounds (e.g., solid bases), reaction accelerators (e.g.,solid acids), catalysts (e.g., Fe₂O₃, TiCl₃), ignition materials(described below), thermally conductive materials (e.g., metals,graphites and composites thereof), and so on. Preferably the pellets donot include a catalyst for the hydrogen-generating reaction(s).

The cartridge includes a plurality of heat transfer members (referred tobelow as heat concentrators) for improving the transfer of heat to thehydrogen containing material, particularly material that is not incontact with the casing. The heat concentrators are solid (e.g., nothollow) and do not penetrate the casing. Each pellet is in contact witha heat concentrator, a portion of which can extend beyond the pellet tomake direct contact with the casing. The heat concentrator conducts heatapplied by a heating element to an adjacent opposite outer surface ofthe casing to the solid composition of the pellet. The heat concentratorcan be in pressure contact with an inside surface of the cartridgecasing (i.e., an inside surface of the casing side wall, bottom or lid).Good contact between the heat concentrator and the casing provides goodheat transfer while facilitating manufacture of the cartridge.Preferably the heat concentrator will have a relatively largeinterfacial contact surface with the casing compared to the thickness ofthe casing so the majority of the heat from the heating elements will beconducted through the casing to the heat concentrator rather than alongthe casing wall.

The heat concentrator can be disposed on a surface of the pellet, or itcan be partially disposed within the solid composition. For example, aheat concentrator disposed on a surface of the pellet can be in the formof a strip or sheet extending beyond the outer edge or side of thepellet. The protruding edge can be bent along that edge or side, therebyincreasing the interfacial surface area with the casing and/or providinga spring-like pressure contact portion. The portion of the heatconcentrator that does not extend beyond the edge of the pellet can beflat or have a bent or curved shape. Alternatively, the heatconcentrator can be in the form of a cup in which the pellet isdisposed, with the peripheral wall of the cup making contact with thecasing. One or more heat concentrators can be used to conduct heat tohydrogen containing material in a single pellet, or a single heatconcentrator can conduct heat to hydrogen containing material in morethan one pellet. In a variation, the heat concentrator can includemultiple strips extending beyond the edge of the pellet, with the stripsinterconnected in an area inward from the edge of the pellet (e.g., witha configuration similar to a leaf rake with tines that are joinedtogether near the handle). This type of configuration can distribute theheat broadly to the pellet with a reduced volume, providing more spacefor the solid composition of the pellet and consequently more hydrogencontaining material in the hydrogen generator. More than one pellet canshare the same heat concentrator (e.g., so more than one pellet can beheated at one time). In some embodiments, one heating element may beprovide heat to more than one heat concentrator (e.g., if an individualpellet has more than one heat concentrator, or if it is desirable toheat more than one one pellet at one time).

Both the heat concentrator and the portion of the casing the heatconcentrator contacts are made of materials with good thermalconductivity and capable of withstanding high temperatures. Thecartridge casing will also be capable of remaining sealed during use.Suitable materials for the heat concentrator and the portion of thecasing include graphite, heat pipes, metals such as aluminum, copper,silver and stainless steel. Alternatively, a molded thermoset materialloaded with dust or powder of a thermally conductive material (e.g.,metal or graphite). Aluminum is a preferred metal for the heatconcentrator because of its high thermal conductivity and relatively lowcost. The heat concentrator can be a multi-layer material. For example,it can include a layer of the metal (e.g., aluminum) with a coating of amaterial with a very high thermal concuctivity, such as pyroliticcarbon, between the metal and the pellet solid composition. Aluminum andstainless steel are preferred metals for the cartridge casing. When avery high thermal conductivity is desired, aluminum can be used. If alower thermal conductivity is desired, stainless steel can be used.Pyrolytic carbon is a man-made carbon material similar to graphite, butwith graphene sheets crystallized in a planar order and with somecovalent bonding between graphite sheets.

In hydrogen generators where a metal compound in the pellet compositionis reduced to a metal with a high thermal conductivity (e.g., thereduction of alane to aluminum metal), it may be possible to reduce thesize of the heat concentrator in contact with the pellet if the metalproduced will function as a part of the heat concentrator. This can makemore space available for hydrogen containing materials and maintain goodheat transfer to those materials during use of the hydrogen generator.

The heat concentrator can conduct heat directly to the hydrogencontaining material, or an ignition material (a material that will reactexothermally, producing heat necessary for the release of hydrogen gasfrom the hydrogen containing material) can be included in the pellet,such as in a mixture with the hydrogen containing material or as aseparate layer or portion of the pellet. If the release of hydrogen gasfrom the hydrogen containing material generates heat, it may be possibleto reduce or stop applying heat after the release is initiated. Anignition material will react exothermically and can be used tosupplement or replace the application of more heat by the heatingelements, thereby reducing the amount of energy consumed by the hydrogengenerator. The ignition material can be admixed with the hydrogencontaining material or be a separate coating, layer or portion of thepellet. Preferably the ignition material will also produce some hydrogengas when it reacts, adding to the total amount of hydrogen that isreleased. Examples of ignition materials (some of which can alsocontribute to the hydrogen yield) include metal/metal oxide multilayerssuch as Ti/Pb₃O₄, Zr/Fe₂O₃, guanidinium borohydride, B-N compoundsblended with oxidizers such as ammonium nitrate or Sr(NO₃)₂ as describedin US2011/0027168A1, metal/metal multilayered thin films and structuressuch as Ni/Al as described in U.S. Pat. No. 7,867,441, autoignitioncompositions such as silver nitrate mixed with potassium nitrate andmolybdenum metal as described in U.S. Pat. No. 6,749,702, complexhydride, oxidizer, and S compositions such as described in U.S. Pat. No.7,964,111, and the compositions described in patents US2008/0236032A1and US 2008/0241613A1. Other compositions include gels of metals andwater such as Mg/water/poly(acrylamide-co-acrylic acid) alone or incombination with sodium borohydride (Varma, et al. Chem. Eng. Sci 2010,65, 80-87 and Int. J. Hydrogen En 2007, 32, 207-211, respectively).

The pellets can be arranged within the cartridge in a variety of ways.For example, the plurality of pellets can be arranged in a single layeror in a plurality of layers with each layer containing one or more thanone pellet. Factors such as the size and shape of the cartridge,compartment and hydrogen generator, the volume of hydrogen to bereleased by a single cartridge, and simplicity of the initiation systemcan be considered in selecting a pellet arrangement. For example, if thelayers are relatively large it may be desirable to include a pluralityof pellets on each layer in order to enable hydrogen release at a slowerrate, while if the layers are relatively large it may be desirable tohave fewer pellets or only a single pellet on each layer to minimize theamount of thermal insulation required between adjacent pellets.

While it may be desirable to react more than one pellet at a time, inorder to prevent the uncontrolled initiation of reactions in adjacentpellets it is desirable for individual pellets or groups of pellets tobe thermally insulated from one another. This can be accomplished invarious ways, including spacing pellets apart from each other,separating pellet layers with themally insulating material (e.g, sheetsor layers of thermally insulating material), placing thermal insulationbetween adjacent pellets or layers of pellets (e.g., containers orcoatings made of thermally insulating material), and so on. Suitablethermal insulator materials include silica, silicon dioxide, siliconnitrides, silicon carbide, silica aerogel, alumina, alumina oxide,glass, glass wool, mineral wool, cellular glass, perlite, and polymerssuch as polyimides and epoxy-amine composites. Other types of heatingelements may be used.

The heating elements are disposed within the compartment, such as on aninside surface of the compartment housing. This surface, which can be asurface of a wall or a portion of the housing that can be opened orremoved to allow insertion and removal of a cartridge, can define aportion of a cavity into which the cartridge can be inserted. When thecartridge is installed in the compartment, the cartridge and compartmentare positioned such that each heating element is in contact with anouter surface of the cartridge casing and aligned with a heatconcentrator in contact with the casing. The heating elements andadjacent heat concentrators can be directly opposite each other,separated by the casing. There can be a path with high electricalresistance and high thermal conductivity between the heating elementsand the cartridge casing (e.g., a coating on resistive heating elements)to allow heat transfer as well as prevent shorting of the heatingelements. Each heat concentrator can be supplied with heat from a singleheating element, one heating element can be used to supply heat to morethan one heat concentrator, or multiple heating elements can supply toheat to a single heat concentrator. Because the cartridge is removablefrom the hydrogen generator, insertion and removal of the cartridge canbe facilitated if contact between the heating elements and the cartridgecasing is a pressure contact, rather than a welded or other fastenedcontact for example. Examples of suitable types of heating elementsinclude resistive heating elements. Resistive heating elements can bewire, ribbon or strip. Suitable materials include metals and alloys(e.g., nickel-chromium alloys, iron-chromium-aluminum alloys,copper-nickel alloys, and other types of alloys), intermetalliccompounds (e.g., molybdenum disilicides) and metal-ceramics.

It may be desirable to include means for maintaining good contactbetween the solid composition and the heat concentrators in pelletswhile the hydrogen generator is being used, particularly if the densityof the solid composition changes as materials react. It may be desirableto include means for maintaining alignment between the heatconcentrators and their corresponding heating elements in unused pelletsand as pellets are reacted. Biasing elements, such as compression padsand springs, may be useful for these purposes. It may be desirable todesign heat concentrators to also function as biasing members. It may bedesirable to control the sequence of heating individual pellets tominimize the effects of heated pellets on the unused pellets in thecartridge.

The compartment housing is made of a material that can withstand thetemperatures and pressures to which it may be exposed. It can be a poorconductor of heat in order to protect other components of the system aswell as the user from damaging or dangerous temperatures. It can be apoor electrical conductor to prevent short circuiting of the heatingelements and the electrical circuit including them. If it is not amaterial with poor thermal or electrical conductivity, thermal and/orelectrical insulation can be added. Examples of suitable materialsinclude metals such as aluminum, steel, stainless steel and so on, orhigh temperature resistant ceramics and polymeric materials. Examples ofhigh temperature polymeric materials includepolyoxybenzylmethylenglycolanhydride (Bakelite®), polyetheretherketone,polyetherimide, and thermoset injection molded plastics such as epoxies,phenolics, diallyl phthalate and melamine.

When the cartridge is inserted into the compartment it must bepositioned so the heating elements are properly aligned with the heatconcentrators. This can be accomplished by a cooperation between thecartridge and the compartment. For example, the cartridge and thecompartment can be keyed (e.g., portions of the cartridge andcompartment mate with each other, as a key mates with a lock, only whenthe cartridge and the compartment are positioned relative to one anothersuch that the heating elements and heat concentrators are properlyaligned).

If the heating elements on the inner surface of the compartment housingare in pressure contact with the outer surface of the cartridge casing,the heating elements can include spring-like elements that will alloweasy insertion and removal of the cartridge into the compartment.Alternatively, the compartment housing can be oversized relative to thecartridge casing and reduced in size after cartridge insertion andincreased in size for cartridge removal. This can be accomplished in avariety of ways. For example, the housing can have long segmentsseparated by spaces, similar to a collet chuck, that form a collararound the inserted cartridge; a slip ring or other device can be usedto tighten and loosen the segments. In another example, the housing canbe split along its length and be tighted with a clamping device similarto a piston ring compressor or a radiator hose clamp. Alternatively, thehousing can be a split spring-like device similar to a tolerance ringthat is enlarged as the cartridge is inserted and biases the housingagainst the insterted cartridge casing.

An initiation system including the heat concentrators, the heatingelements and circuitry for conducting electric current to the heatingelements, selectively heats one or more pellets at a time to generate adesired quantity of hydrogen gas. This can be done by applying currentto the desired heating element(s) such that the heating element becomeshot and heat is transferred from the heating element, through thecasing, to the aligned heat concentrator, and then to the pellet solidcomposition. The current source can be a battery, fuel cell or othersource of electrical energy within hydrogen generator, elsewhere in thesystem, or even outside the system (e.g, within a device being suppliedwith power from a fuel cell battery in the system).

The initiation system can include one or more monitors for monitoringone or more hydrogen generator, fuel cell battery, fuel cell system ordevice parameters. These parameters can be useful in controlling thehydrogen generator to insure safety and to generate hydrogen on an asneeded basis. The initiation system can include or be included in acontrol system. The control system can be used to control the release ofhydrogen, such as to provide hydrogen gas as needed. This can bedetermined based on one or more criteria, such as pressure (e.g.,internal pressure or a differential between an internal and an externalpressure); temperature (e.g., hydrogen generator, fuel cell or devicetemperature); a fuel cell electrical condition (e.g., voltage, currentor power); or a device criterion (e.g., internal battery condition,power input, or operating mode. The control system can be used for otherpurposes. For example, it can be used to monitor the quantity of fuelremaining in the cartridge and provide related information to the user.It can be used to halt the release of hydrogen gas to avoid unsafeconditions. It can be used to monitor or verify information regardingthe installed cartridge (e.g., to confirm that it is the correct type ofcartridge, has sufficient fuel remaining, and so on). It can provideone- or two-way communication among components of the fuel cell systemand/or a device including the fuel cell system. The control system canbe completely or partially disposed in the hydrogen generator, a fuelcell battery, a fuel cell system, a device being powered by the fuelcell system, or any combination thereof. The control system can includea microprocessor or micro controller; digital, analog and/or hybridcircuitry; solid state and/or electromechanical switching devices;capacitors; sensing instrumentation; and so on.

The hydrogen flow path can include a channel extending through or aroundthe pellets or pellet layers. The channel can be a central channel forexample. Multiple channels can be present. The hydrogen generator caninclude one or more filters and/or purification units to removeundesired reaction byproducts and other contaminants from the hydrogengas. The filter(s) and purification unit(s) can be disposed in thehydrogen flow path.

The hydrogen generator can also include various fittings, valves andelectrical connections for providing hydrogen to and interfacing with afuel cell battery and/or an electrical appliance being provided withpower by the fuel cell system. For example, the hydrogen outlet valve inthe cartridge casing can cooperate with the hydrogen outlet through thecompartment housing so hydrogen gas can be released. The hydrogen outletthrough the housing can be an opening through which the hydrogen outletvalve can extend, or the a connector from another component of thesystem can extend through the opening to couple with the hydrogen outletvalve. Alternatively, the hydrogen outlet can include a connector thatcouples with the hydrogen outlet valve.

The hydrogen generator can include various safety features such as apressure relief vent to release excessive pressure and a mechanism tostop the initiation system if the internal temperature or pressureexceeds an established limit.

To help maintain a tight seal before use and to indicate an unusedcartridge, a seal, such as a foil seal, can be placed over the hydrogenoutlet valve. The foil seal can be removed before inserting thecartridge into the compartment, the seal can be broken by inserting thecartridge into the compartment, or internal pressure from the hydrogengas released when the cartridge is used can force the seal open.Alternatively, the cartridge can be packaged in a hermetically sealedcontainer and removed before use.

In embodiments of a hydrogen generator in which more than one cartridgecan be contained, the hydrogen generator can be designed to operate withless than the maximum number of cartridges inserted. The individualcartridges can be accessible through a single access (e.g., lid, door orthe like) or multiple accesses. It can be advantageous for cartridges tobe separately replaceable while the hydrogen generator is operating inorder to provide for continuous operation, without shutting down toreplace spent cartridges.

FIGS. 1, 2 and 3 illustrate an embodiment of a hydrogen generator.Hydrogen generator 10 is shown as a cylindrical device; however, itssize and shape can be varied as described above. In addition, specificfeatures shown in FIG. 1 can be deleted or modified, and other featurescan be added, as described above. Hydrogen generator 10 has acompartment 12 with a housing including a side wall 14, a lid 16 and adoor (not shown) that define a cavity into which a cartridge 20 can beremovably inserted. In FIG. 1 the cartridge 20 is inserted into thecompartment 12, and in FIG. 2 the cartridge 20 is not inserted into thecompartment 12. The cartridge 20 has a casing with a side wall 22, abase wall 24 and a lid 26. The base wall 24 can be a separate componentthat is secured to the side wall 22 (e.g., with an adhesive or by laserwelding), or the base wall 24 and the side wall 22 can be portions of aunitary can. The lid 26 can be separate component that is secured to theside wall 22 (e.g., with an adhesive or by laser welding), or the lid 26and the side wall 22 can be portions of a unitary can. The cartridge 20includes a hydrogen outlet valve 28 secured to the lid 26 (e.g., with aglass-to-metal seal). When the cartridge 20 is installed in thecompartment 12, the hydrogen outlet valve 28 can be coupled to theremainder of the system (not shown). The hydrogen outlet valve 28 can berecessed within the compartment 12 and accessed through an opening 30 inthe compartment lid 16, the hydrogen outlet valve 28 can extend throughthe opening 30 to the outside of the hydrogen generator 10, or thehydrogen outlet valve 28 can mate with a coupling 32 in the opening 30of the compartment lid 16, as shown in FIGS. 1, 2 and 3.

Within the cartridge 20 is a plurality of pellets 40. Each pellet 40includes a solid composition 42 that contains a hydrogen containingmaterial. Each pellet 40 also includes a solid heat concentrator 44 forconducting heat to the solid composition 42 without penetrating thecasing. As shown in FIGS. 1, 2 and 3, the heat concentrator 44 is in theform of a shallow cup containing the solid composition 42 of the pellet40. The peripheral wall of the cup is in direct contact with thecartridge side wall 22. The pellets 40 are arranged in layers in thecartridge 20. A layer of thermal insulation, such as an insulation disc46 can be included to separate the layers of pellets 40 if necessary, toprevent heat from one pellet layer from unintentionally causing areaction in an adjacent pellet layer. As shown in FIGS. 1, 2 and 3, eachlayer includes multiple pellets 40, with thermal insulation such asinsulating layer 58 separating adjacent layers.

On the inner surface of the compartment side wall 14 is a plurality ofheating elements 50. When the cartridge 20 is inserted in thecompartment 12, the heating elements 50 are in direct contact with thecartridge side wall 22 and aligned on the opposite side of the cartridgeside wall 22 from the peripheral walls of the heat concentrators 44.

As the pellets 40 are heated, the hydrogen gas released flows through ahydrogen flow path, which can include a central channel 52. A guideplate 54 can be used to direct the hydrogen to an entry to one or aseries of filters 56 through which the hydrogen travels before reachingthe hydrogen outlet valve 28. The filters 56 remove solid particles(e.g., reaction byproducts and pieces of unreacted reactant) that may becarried away from the pellets 40 by the hydrogen gas. A purificationunit (not shown) can also be disposed in the cartridge before thehydrogen outlet valve 28 or elsewhere (e.g., outside the outlet valve28) to remove contaminants such as undesired gaseous byproducts andimpurities) from the hydrogen gas.

An electric circuit 60 can carry current to selected heating elements 50to heat selected heat concentrators 44 and cause the solid composition42 to react. The source of the electric current can be outside thehydrogen generator 10. External electrical contacts 62 can make contactwith the circuit 60 to provide electric current from the source to thecircuit 60.

A second embodiment of a hydrogen generator is shown in FIG. 4. Hydrogengenerator 210 has a prismatic shape and includes a compartment 212 and acartridge 220 that can be removably inserted into the compartment 212.The compartment 212 includes a housing, which can have any suitabledesign, such as opposing trays 214 a and 214 b as shown in FIG. 4. Thecartridge 220 includes a plurality of pellets 240, each including asolid composition 242 containing a hydrogen-generating material andincluding a heat concentrator 244 for conducting heat to the solidcomposition 242. The pellets 240 are contained in a casing 222(generally represented in FIG. 4 with dashed lines) with a hydrogenoutlet (not shown). The heat concentrators 244 are aligned withcorresponding heating elements 250 when the cartridge 220 is installedin the compartment 212. Heat is conducted from the heating elements 250,through portions of the casing 222, and then via the heat concentrators244 to the solid composition 242 of the pellets 240. The heatconcentrators 244 make contact with but do not pass through the casing222 and extend into the pellets 240, as shown in FIG. 5. The heatconcentrators 244 are shown having a cylindrical shape but may be ofother shapes. Each of the pellets 240 has a prismatic shape, such as thepyramidal shape shown in FIG. 4, with the heat concentrator 244protruding from the large end. This arrangement can provide for uniformheat distribution to the solid composition 242 within the pellet 240 andcan provide efficient heating with minimal heat loss by heating from theinside of the pellet 240. Thermal insulation can be provided betweenadjacent pellets 240 to prevent initiation of the hydrogen-generatingreaction in one pellet 240 by an adjacent pellet 240 and allow heatingof only selected pellets 240. Adjacent pellets 240 can oriented inopposite directions as shown to provide efficient utilization of thevolume of the cartridge 220.

A third embodiment of a hydrogen generator is shown in FIG. 6. Hydrogengenerator 310 is similar to hydrogen generator 210 in FIG. 4, but inFIG. 6 the pellets 340 have heat concentrators 344 on external surfacesof the pellets 340. An embodiment of the cartridge 320 is shown in FIG.7, and a pellet 340 is shown before and after assembly of the heatconcentrator 344 and solid composition 342 in FIGS. 8 and 9,respectively. As shown in FIGS. 6 to 9, the heat concentrators 344 areonly on external surfaces of the pellets 340; however, the heatconcentrators can also be shaped to extend into the solid composition342 (e.g., with inward projecting barbs).

A fourth embodiment of a hydrogen generator is shown in FIG. 10.Hydrogen generator 410 is similar to hydrogen generators 210 and 310,with prismatic pellets 440 each including a solid composition 442containing the hydrogen-generating material and a heat concentrator 444for conducting heat to the solid composition 442. The pellets 440 inthis embodiment have a triangular cross section. A cartridge casing 422,which can have two opposing halves 422 a and 422 b, is shown in FIG. 10.The casing 422 can be made from a material that is a poor thermalconductor with thermally conductive areas (not shown) corresponding tothe heating elements 250 when the cartridge 420 is contained within thecompartment 212, so pellets 440 can be selectively heated by thecorresponding heating elements 250. FIG. 11 shows the pellets 440 lowerhousing half 422 b from FIG. 10, and FIG. 12 is a partially explodedview of the assembly in FIG. 11, showing three of the four rows ofpellets in FIG. 11. Thermal insulation 446 is disposed in each row ofpellets 440, between the adjacent pellets 440, and thermal insulation isalso disposed between adjacent rows of pellets 440. The pellets 440 andthermal insulation 446 of one row of pellets 440 are shown in theexploded view of FIG. 13, and a single pellet 440 is shown in FIG. 14.Another embodiment of a pellet 445 that can be used in the hydrogengenerator 410 is shown in FIG. 15, where the heat concentrator 445 hasbeen modified to include a plurality of connected fingers. FIG. 16 is anon-exploded, cross-sectional view of the hydrogen generator 410 in FIG.10. The heat concentrators 444 are disposed against the top and bottomcasing halves 422 a, 422 b, which are disposed against the heatingelements 250 to provide good heat transfer from the heating elements250, through the casing halves 422 a, 422 b and corresponding heatconcentrators 444 to the solid composition 442 of the pellets 440.

Another embodiment of a hydrogen generator is shown in FIGS. 17 and 18.in this embodiment, hydrogen generator 510 is configured to accommodatea plurality of cartridges 520. The hydrogen generator 510 has acompartment 512 with a side wall 514 and a lid 16 that can be opened toinsert cartridges 520 and remove the cartridges 520 after they have beenused. Heating elements 550 are disposed on the inside surface of thehousing side wall 514 such that the individual pellets 540 will bealigned with the heating elements 550 when the cartridges 520 aredisposed in the hydrogen generator 510. Alignment features 566 canextend from the inner surface of the housing side wall 514 to facilitateproper of alignment of the pellets 540 with the heating elements 550.The alignment features 566 can also separate the cartridges 520,creating channels 553 between the cartridges 520. Each cartridge 520includes a stack of individual pellets 540 within a casing, which canhave a side wall 522 and a base wall 524. The casing includes sectionsthat are good conductors of heat from the heating elements 550 to thepellets 540. The solid composition of the pellet 540 contains a hydrogencontaining material. The hydrogen containing material can be in directcontact with the casing side wall 522 and/or a heat concentrator 544disposed on the surface of and/or within the pellet 544. When a pellet540 is heated by a heating element 550, hydrogen gas is released andtravels through a hydrogen flow path to a hydrogen outlet 528. Thehydrogen flow path can include one or more channels, such as centralchannel 552 and channels 553 between the cartridges 520. A filter 556,which can include one or multiple filter elements, can be disposedwithin the hydrogen flow path to remove solid contaminants from thehydrogen gas. A plate 554 can be present in the housing 512 to supportthe filter 556 and guide the hydrogen so it will flow through the filter556 before reaching the hydrogen outlet 528. Thermal insulation can bedisposed between adjacent pellets 540 to prevent heat from one pellet540 from causing hydrogen containing material in an adjacent pellet 540from releasing hydrogen gas. The thermal insulation can be disposedbetween pellets in a stack, such as insulating discs 546, thermalinsulation can be coated on surfaces of the pellets 540, and thermalinsulation can be disposed in channels such as channels 552 and 553around the pellets 540 and fuel units 520. The thermal insulation can beporous material that will allow hydrogen gas to flow therethrough. In avariation of the embodiment in FIGS. 17 and 18, the cartridge casing cancompletely enclose the pellets 540 therein, with one or more passages inthe casing through which hydrogen can pass or with at least a portion ofthe casing being hydrogen permeable. Although hydrogen generator 510 isshown with multiple cartridges 520 in a single cavity within thecompartment 512, compartment 512 can be divided into multiple cavities,such as by extending alignment features 566 inward. The compartmenthousing door 564 can also be modified to provide separate access toindividual or groups of cartridges 520.

All references cited herein are expressly incorporated herein byreference in their entireties. To the extent publications and patents orpatent applications incorporated by reference contradict the disclosurecontained in the present specification, the present specification isintended to supersede and/or take precedence over any such contradictorymaterial.

It will be understood by those who practice the invention and thoseskilled in the art that various modifications and improvements may bemade to the invention without departing from the spirit of the disclosedconcept. The scope of protection afforded is to be determined by theclaims and by the breadth of interpretation allowed by law.

1-20. (canceled)
 21. A method of generating hydrogen gas comprising:disposing a plurality of pellets within a cartridge, each pelletcomprising at least one hydrogen containing material capable ofreleasing hydrogen gas when heated, said cartridge comprising: a casing;a plurality of solid heat transfer members, each in direct contact withbut not penetrating the casing; a hydrogen outlet valve in the casing;and a hydrogen flow path from each pellet to the hydrogen outlet valve;wherein the plurality of solid heat transfer members are configured sothat when heat is applied to a portion of the casing in direct contactwith one or more solid heat transfer members, the solid heat transfermembers transfer heat to one or more pellets to initiate a release ofhydrogen gas; disposing the cartridge within a cavity of a compartment,said compartment configured to removably contain the cartridge, thecompartment comprising: a housing comprising a wall; a hydrogen outletthrough the housing; and a plurality of heating elements disposed withinthe housing such that when the cartridge is disposed within the cavityeach heating element is in contact with a portion of the outer surfaceof the cartridge casing; selectively applying electrical current to oneor more heating elements to heat one or more portions of the outersurface of the cartridge casing in contact with one or more of the solidheat transfer members of the cartridge.
 22. The method of claim 21,wherein the selectively applying electrical current comprises using aninitiation system comprising the heat transfer members, the heatingelements, and circuitry for conducting an electric current to theheating elements.
 23. The method of claim 21, wherein the cartridge andthe compartment are configured so that the cartridge can be insertedinto the compartment only such that the heating elements and the heattransfer members are aligned for conducting heat from the heatingelements, through the casing, and to corresponding heat transfermembers.
 24. The method of claim 21, wherein at least a portion of eachheat transfer member is disposed on a pellet surface.
 25. The method ofclaim 24, wherein the heat transfer members are partially disposedwithin the pellets.
 26. The method of claim 21, wherein each heattransfer member has a portion that contacts the cartridge casing. 27.The method of claim 21, wherein each heat transfer member includes alayer of pyrolytic carbon in contact with a pellet.
 28. The method ofclaim 21, wherein the heat transfer members are in pressure contact withan inside surface of the casing.
 29. The method of claim 21, wherein thepellets are disposed in one or more layers and a thermally insulatingmaterial is disposed between adjacent pellets in the one or more layersof pellets.
 30. The method of claim 29, where in a layer of thermallyinsulating material separates each pair of adjacent layers of pellets.31. The method of claim 30, wherein pellet surfaces are coated with alayer of the thermally insulating material.
 32. The method of claim 21,wherein the cartridge comprises means for maintaining contact betweenthe heat transfer members and the pellets.
 33. The method of claim 21,further comprising enclosing the cartridge in the casing prior to thedisposing the cartridge within the cavity of the compartment.
 34. Themethod of claim 21, wherein the disposing the plurality of pelletswithin the cartridge forms a plurality of layers of pellets.
 35. Themethod of claim 34, wherein each layer comprises a plurality of pellets.36. The method of claim 21, wherein the disposing the plurality ofpellets within the cartridge forms a single layer of pellets.
 37. Themethod of claim 21, wherein the plurality of pellets does not include acatalyst for the release of hydrogen gas.
 38. The method of claim 21,wherein the casing comprises two opposing halves; and the casingcomprises a material that is a poor thermal conductor with thermallyconductive portions configured to align to the heating elements when thecartridge is disposed within the compartment.
 39. The method of claim38, further comprising sealing the casing so that it remains sealedduring the generating of hydrogen gas.
 40. The method of claim 21,wherein the pellets further comprise at least one ignition materialselected from the group consisting of metal/metal oxide multilayers, ametal/metal multilayered thin film, an autoignition composition, a gelof a metal and water, and a gel of metal and water in combination withsodium borohydride.
 41. A method of generating power comprising:providing hydrogen gas generated according to the method of claim 2 to afuel cell battery.
 42. The method of claim 41, wherein a portion of theinitiation system is outside the compartment.
 43. The method of claim42, wherein the initiation system is configured to monitor at least oneof temperature and pressure and configured to selectively heat one ormore pellets to provide hydrogen gas as needed by the fuel cell battery.